Fractal Model Of Static Friction Coefficient Of Joint Surfaces Based On Multiscale Contact

Equipment manufacturing is one of China’s major strategic plans in China2025.High-grade CNC machine tools with high performance,high precision and high stability is a development priorities of Equipment manufacturing.The universal joint surface in the machine tool structure is an important factor,which affects the load and energy transfer.This paper mainly focuses on the theoretical modeling of the static friction coefficient.The main work is listed as follows:(1)The height of the asperity and the deformation of the asperity are strictly distinguished.Based on the contact parameters of the asperity and the relationship between the elastic critical deformation,the elastic critical contact area,the elastic contact load and the scale number of the asperity,the calculation formula of the static friction coefficient of the asperity is given,and the influence of the normal contact load of the asperity on the static friction coefficient is simulated and analyzed.(2)Based on ME multi-scale contact fractal model and single micro-convex contact static friction coefficient calculation formula,a two-dimensional fractal model of joint surface static friction coefficient based on multi-scale contact is established,and the model is numerically simulated.The analysis reveals the relationship between joint surface static friction coefficient and joint surface non-dimensional normal contact load,non-dimensional real contact area.The results show that joint surface static friction coefficient decreases with the increase of joint surface non-dimensional normal contact load.(3)On the basis of the above work,a 3D fractal model of the static friction coefficient of the joint surface based on multi-scale contact is established based on the 3D fractal contact theory of the joint surface,and compared with the 2D fractal model through simulation calculation.The two models have the same regularity,but slightly larger than the value of the 2Dfractal model.(4)The fractal model of static friction coefficient of joint surface based on multi-scale contact,statistical model of static friction coefficient of joint surface and Bhushan experimental data are compared and analyzed to verify the correctness and effectiveness of the model.